Quality of service (QoS) is an important consideration in wireless communication systems. Different types of service require different levels of quality. For example, a mobile telephone user that is engaged in a voice call with a network will likely require a higher quality connection (in terms of delay) than a user that is web surfing on his or her mobile telephone. Likewise, a user engaged in a web surfing session will likely require a better bit error ratio than a user engaged in a voice call. In accordance with existing 3rd Generation Partnership Project (3GPP) standards, when a user equipment (UE), such as a mobile telephone, requests service from the core network (CN), a UMTS bearer service and underlying radio access bearer (RAB) service is set up for the requested service. This protocol is described in sections 6.1, 6.1.1, 6.1.2 of 3GPP TS 23.107 v4.0.0 (2000-12). Presently, the RAB includes nineteen (19) parameters for the service such as traffic class, maximum bit rate, and guaranteed bit rate, to name a few. The parameters characterize the required QoS for the requested service.
The RAB parameters are defined in section 9.2.1.3 of 3GPP TS 25.413 v4.0.0 (2001-03). The traffic class is defined as the type of application for which the Radio Access Bearer service is optimized. The maximum bit rate is defined as the maximum number of bits delivered by the Universal Terrestrial Radio Access Network (UTRAN) and to the UTRAN at a Service Access Point (SAP) within a period of time, divided by the duration of the period. The guaranteed bit rate is defined as the guaranteed number of bits delivered at a SAP within a period of time (provided that there is data to deliver), divided by the duration of the period. In accordance with sections 8.2 and 9.1.3 of TS 25.413, a RAB Assignment Request message with specified RAB parameter values is sent from the CN to a Radio Network Controller (RNC) in the UTRAN to inform the RNC of the QoS expected by the CN for a RAB. If any of the RAB parameters need to be changed, RAB negotiation or renegotiation/reconfiguration is performed. RAB negotiation refers to the exchange that occurs at the establishment of a RAB before settling on RAB parameter values. RAB renegotiation/reconfiguration refers to the exchange that occurs after the establishment of a RAB to request change of some or all previously agreed upon RAB parameter values.
In 3GPP Release 1999 standards, such as TS 24.008, v3.7.0 (2001-03), section 6.1.3.3 on PDP context modification procedure, QoS renegotiation for a service can be initiated by the CN and the UE. This does not allow efficient management of radio resources, because although the RNC actually manages the radio resources, it is not allowed to initiate QoS renegotiation through RAB renegotiation/reconfiguration to account for changed radio conditions. Failure to perform RNC initiated RAB renegotiation/reconfiguration can result in radio network overload, dropped calls and degradation of the quality of remaining calls. For example, if the RAB for a call initially specifies a maximum bit rate of 16 kbps, the RNC may need to lower the maximum bit rate to 12 kbps due to changed radio conditions. Currently, the RNC is unable to initiate renegotiation/reconfiguration of the RAB to effect this change which could result in a dropped call. Thus, there is a need for a method of RNC initiated RAB renegotiation/reconfiguration to decrease the occurrence of radio network overload, dropped calls and degradation of call quality.